1.Field of the Invention
This invention generally relates to semiconductor devices and, more particularly, to a semiconductor device which can be mounted on a circuit board so that the semiconductor device stands vertically.
In recent years, a surface mounting package has been widely used in which a semiconductor device is soldered on a circuit board, rather than to provide holes made to in the circuit board which are used to solder leads thereon. A package placed vertically on the mounting surface of the circuit board (hereinafter referred to as a "vertical package") is known in order to increase the density of mounting on the circuit board.
It is desired to achieve a package which has the advantages of both the surface mount package and the vertical package.
2. Description of the Prior Art
A semiconductor device having a package structure having the advantage of the surface mount package and the advantage of the vertical package is disclosed in Japanese Laid-Open Patent Publication No. 2-21645. FIG. 1 shows a semiconductor device 1 disclosed in the above application.
In FIG. 1, a resin package 2 houses a semiconductor device 3. Inner lead portions 4a of leads 4 are connected with the semiconductor device 3, and the outer lead portions 4b thereof extend out of the package 2. Further, predetermined tip portions of the outer leads 4b are bent at the same angle.
Spacers 5 are placed on the opposite ends of the section (i.e., edge) of the package from which the outer leads 4b of the package 2 extend. Each of the spacers 5 includes a clip 6 and a cylinder part 7 with the diameter contractible. The spacers 5 are used, as shown in FIG. 2, to mount the semiconductor device 1 on a circuit board 8.
Slots, or holes, 8a, with which the relevant cylinder parts 7 are to be engaged are formed on the circuit board 8. The semiconductor device 1 is made to stand vertically on the circuit board 8 by engaging the cylinder parts 7 with the slots 8a of the spacers 5. The outer leads 4b are soldered to a pattern 8b formed on the circuit board 8.
However, with the semiconductor package 1, the slots 8a are needed to vertically place the semiconductor packages 1 on the circuit board 8. Unlike normal surface mount packaging, the holes 8a have to be formed before mounting. This is a problem because it reduces mounting efficiency.
Also, as shown in FIG. 2, the outer lead 4b extends for a relatively long distance toward the circuit board 8 and is bent. The bent portion of the outer leads 4b is soldered to the pattern 8b formed on the circuit board 8. That is, the outer lead 4b has a long portion extending out of package 2. External disturbances may enter through this exposed portion, which may prevent favorable transmission of signals between the semiconductor device 1 and the circuit board 8.
The applicant has proposed, as set forth in Japanese Laid-Open Patent Application No. 4-52434, a semiconductor device with a structure in which a resin package is placed vertically on a circuit board and connection leads are bent in the vicinity of the resin package in order to support the resin package with supporting leads extending in opposite directions from each other.
However, with the demand for down-sizing of electronic devices in recent years, there has been a increasing demand for down-sizing of semiconductor devices, which are structural components, and thereby to achieve an increase in the integration density. The demand for the increased density has been accommodated by efforts toward providing an increased number of pins. Particularly, in packages having a large number of pins, such as a QFP (Quad flat package) and PGA (Pin Grid Array), an effort has been made to reduce the terminal pitches and increase the number of pins in order to enhance the integration density.
However, since the packages proposed by the above Japanese publication and application use a single in-line package, there is a potential problem in that the increased number of pins will elongate the package in the direction of pin alignment and that the resulting extended mounting area on the circuit board will make it difficult to mount the device on a smaller circuit board.